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Discussion Starter #1
I had unloaded my M&P mags and noticed two of the rounds looked shorter than the rest. I checked and sure enough, the two bullets has been pressed back into their cases.



I have noticed that when I release the slide slowly, as the slide strips a round from the magazine, the round nose dives into the feed ramp and will hold the slide open. Although I have never had a feed problem while shooting or if I drop the slide at full speed, the nose dive does concern me.



Bullets that set-back in the case will fire, but will also cause higher camber pressures and possible 'fliers'. How do we know this isn't happening while shooting?



Of course one thing that purportedly circumvents the issue is dropping the slide cleanly at full speed. But even that makes me wonder if it happens at slower speeds, why doesn't it also happen at full force/speed?



Any thoughts?
 

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Its normal to have two bullets with set back. Its potentially dangerous, but it's normal, as repeatedly loading and unloading a pistol will make you use the same two rounds. Change out your ammo more often.



About how you drop the slide, all kinds of bad things can happen when you ride the slide forward slowly and obviously it does not mimic the movement of the slide while shooting. Last year there was a deputy that was involved in a shooting and, according to the investigation, she rode her slide forward, the gun jammed, and she was killed.



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Discussion Starter #3
Normal? I've never seen this on Glocks, XDs, Sigs, Berettas, H&Ks, or other S&W semi-autos. I have not loaded/unloaded my M&P any differently or more or less frequently than any of the guns mentioned above - this has only happened with my M&P, well and 1911s.



I, like many, have carried the same SD ammo in a gun for up to a year and never seen this problem on any other gun. I have unloaded/reloaded the top two rounds alternately in other guns and never had a set back issue.



I know I can ignore the problem by dropping the slide cleanly, I just wonder if that actually fixes the problem, or we just aren't aware that the bullet is taking a beating.
 

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Tangle said:
Normal? I've never seen this on Glocks, XDs, Sigs, Berettas, H&Ks, or other S&W semi-autos. I have not loaded/unloaded my M&P any differently or more or less frequently than any of the guns mentioned above - this has only happened with my M&P, well and 1911s.



I, like many, have carried the same SD ammo in a gun for up to a year and never seen this problem on any other gun. I have unloaded/reloaded the top two rounds alternately in other guns and never had a set back issue.



I know I can ignore the problem by dropping the slide cleanly, I just wonder if that actually fixes the problem, or we just aren't aware that the bullet is taking a beating.
This is a well known problem, and has been recognized in all brands of semi auto pistols, there are even specific warnings out for Glocks, see the link below for more info.



http://www.thegunzone.com/glock/setback.html
 

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Discussion Starter #5
Got any documentation of this well known problem other than the Gun Zone?



Guys, I'm not trying to make a fuss out of nothing, but, I've been shooting and carrying for years and shoot between 10,000 and 12,000 rounds a year and never had a set back. Now I get an M&P and have two. The only thing that's changed is the gun.



I think I'll lower the slide 20 times on a JHP in my Sig, another 20 times on another round in my Beretta, then 20 times on another round in my Glock, and then 20 times on another round in my H&K USP and then 20 times on another round in the M&P. Then I'll measure the set back of each with a caliper.



That should tell the tale.
 

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Tangle, I think everyone has probably noticed a set back bullet at one time or another. In case anyone doesn't realize it the feeding of a semi auto pistol or rifle is not a delicate affair. The round is getting moved different directions and smashed into an openning with great force. This is NOT a M&P specific problem. I have noticed it on several pistols when the top round and the round in the chamber are loaded more than twice.
 

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Discussion Starter #7
I'll run my experiment and we'll see what we'll see.



I've never noticed rounds nose diving in any of my other guns. I've never seen one literally lock the slide open other than the M&P. I watch my M&P cycle a round and it nose dives into the feed ramp. It's the only gun I own that does that. And it's the only gun that I've had set back problems with.



I'm gonna take a close look at my Sigs, Berettas, XDs, H&Ks, and Glocks to see if they exhibit this nose dive thing and if I can get them to lock the slide open. But I almost know what I'm gonna find; they don't do it. But I'll do it anyway just to be sure.
 

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I first noticed bullet setback about 30 years ago in a 1911, I observed this happening in several different pistols of various brands and calibers, it was enough that I made a personal rule to rotate my carry ammo, keep it fresh and don't constantly rechamber the same rounds.
 

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Okay I have a polished feed ramp on my M&P, but even before I had that work done, I could not no matter how slowly I fed a round into the chamber, get it to "hang".



Some people have complained of this, what gives? I really doubt that the feedramp angles can vary that much from pistol to pistol.



That said, I saw the worst setback I had ever seen in my life on an XD40 two weeks ago. My buddy had just bought it, and it kept failing to feed. Some of the rounds looked like midgets compared to the others. Scary stuff. These were factory loads but I suspected weak crimps.
 

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Discussion Starter #12
ClosetCaseNerd said:
Okay I have a polished feed ramp on my M&P, but even before I had that work done, I could not no matter how slowly I fed a round into the chamber, get it to "hang".



Some people have complained of this, what gives? I really doubt that the feedramp angles can vary that much from pistol to pistol.



That said, I saw the worst setback I had ever seen in my life on an XD40 two weeks ago. My buddy had just bought it, and it kept failing to feed. Some of the rounds looked like midgets compared to the others. Scary stuff. These were factory loads but I suspected weak crimps.


There ya go! I'm wondering the same thing.



I think we all realize that we won't see a problem if we don't ride the slide, and we shouldn't ride the slide anyway. But, just because we don't ride the slide doesn't mean the rounds aren't nose diving and if they are, they may very well be getting some set back that we don't realize, and we may be shooting them with a little set back.



Does it hurt any thing? I don't know. I suspect though a round with set back raises chamber pressure and changes bullet velocity. Does that hurt anything? I don't know. Is it a good thing? probably not.



But I can say this. If 'soft' load a round twenty times in one gun with no set back and then do the same thing with a new round 20 times in my M&P and I do get set back, it's certainly worth knowing. That would dictate about how often ammo should be loaded/reloaded and that we want to be sure that we are not reloading the same round over and over in an M&P.



Just for clarity, the M&P is my carry gun of choice. It has only had one mal in 1550 rounds and I'm convinced that was a fluke that will never happen again.
 

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Tangle said:
Got any documentation of this well known problem other than the Gun Zone?


We have a law enforcement bulletin at the LEC that I work at.

It is specifying Glocks as having the problem.

I think most of us are all smart enough to know that bullets that hit the

feedramp enough times are possible candidates for "setback".

Depends on bullet crimp and other loading factors when the

bullet is manufactured.

This bulletin just recently came out, crap I've known this for years.

It just kills me to see it being blamed on a specific brand of firearm.

Kinda like the Firestone tires that would cause my SUV roll in the late 90's.
 

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40 S&W is the highest pressure cartridge compared to 9mm and 45 acp and poses the biggest risk, bullet setback can increase pressures tremendously, if you can see a setback on a bullet it's best not to shoot it.
 

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[/quote]

Firestone tires that would cause my SUV roll in the late 90's.[/quote]



the problem was never with Firestone but ford. A tire with a six ply load rating cant be run under pressure like atg the 28 psi recomended by ford compared to the 44 psi. Hence the tire suffers seperation and is prone to impact breaks that cause blow outs.



But back to the subject. When i was looking at getting a glock 22 i did a lot of research especially on the Kaboom factor. One article i came across was one from Los Alamos where security had had a Kaboom in the glock 22. It was later found that they shared the same duty weapon and during the time the same round started in the top of mag and was ejected and reloaded at the end of each shift. if you look hard enoigh you can find the article and in that it talks about setback and that because the loads were no rotated.
 

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Firestone tires that would cause my SUV roll in the late 90's.[/quote]



the problem was never with Firestone but ford.[/quote]



Exactly, ever put an Explorer into a slide? I don't care what kind of tire you

have on, that bad boy wants to roll. Been there done it.



Yes, our bulletin at work shows a Glock 22 with lots of kaboom damage.

This bulletin makes reference to rotating your ammo and keeping an eye on

the top 2 rounds.
 

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Discussion Starter #17
So Glock 22s AND M&Ps have a potential set back problem. That might explain why I've seen two in my M&P. I wonder if that means that every time a round is chambered it is actually set back a bit or does it all happen at once after a number of times of chambering the same round.



Seems like Kabooms were highly associated with the .40 cal. Glocks. Set back could explain that. Anybody hear of bullet set back in the 9mm Glocks?



How about 9mm Sigs, Berettas, or H&Ks?
 

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Riding the slide of any semi-auto changes the dynamics of the loading cycle. The exact changes in any given weapons system varies according to several possible variables. Angle of magazine feed lips, the feed ramp angle, distance from nose of the bullet to feed ramp, magazine spring tension...I think you get the picture. If the slide is moving faster, the round being loaded is much less likely to nosedive, the force stripping it from the magazine is higher, the speed faster. SO, let that slide bang home-it's what happens every time you fire the weapon anyway.



Whoever posted that the loading cycle isn't gentle is very correct. As an example, the 1911-with stock feed ramps- puts rounds into the chamber in a 2 cushion shot. The slug hits the feed ramp, then the roof of the chamber.



Bullet setback is a recognized issue. It can vary between brands and individual lots of ammo.
 

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Discussion Starter #19
Guys, I've seen the cut-away illustrations of a round loading into a semi auto at full speed. There has never been a question that the loading cycle of a semi-auto is harsh. The issue here is simple. I've carried Sigs, H&Ks, Berettas, Glocks, and XDs for some 10 years and never had a single set back in 9mm. I carry an M&P for 3 months and have two bullet set backs.



So I look into the problem and discover that when a round feeds into the chamber, it literally nose dives into the ramp. This morning I compared that to a Glock, an H&K, and a Beretta 92FS. Guess what? They don't make the bullet nose dive. The round in all three of these guns feed straight into the feed ramp, rather than nose down.



So let's think about that. The gun that forces the nose of the round downward into the feed ramp has produced two set backs. The guns that don't do that, have produced none, well in my years of carrying.



If we're going to say that we need to rotate our ammo regularly, and that has been offered as a solution to the problem, it infers that the reason to rotate ammo is because if you don't, you will get bullet set back. So it's not like the problem doesn't exist and it's not like dropping the slide at full speed fixes the potential problem. If it did, you wouldn't need to rotate ammo.



As far as dynamics go, sure bullet dynamics change as feed speed changes. So to determine where the bullet strikes the feed ramp in a full speed load, I'll color my feed ramp with a magic marker and see where the bullets strike the feed ramp when chambered at full speed.



Then for the claims that all guns do that. I have to disagree and say some guns do that and some do it worse than others. I'm not trying to bash the M&P at all; without the set back problem, that'd be the only gun I'd carry. I like it that much. OTOH, if it has a problem that's more pronounced than other high quality guns, I want to know that. I can just about guarantee that if I cycle the same round 20 times in an M&P AT FULL SPEED, there will be significant bullet set back. And I'd be willing to bet that if I did the same thing with an H&K, Glock, Beretta 92FS, or Sig there will be NO bullet set back.



I'll try to do that when I get some time.
 

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Firestone tires that would cause my SUV roll in the late 90's.[/quote]



the problem was never with Firestone but ford



IAShooter said:
Exactly, ever put an Explorer into a slide? I don't care what kind of tire you

have on, that bad boy wants to roll. Been there done it..


Of course thats why my 05 Explorer hads roll stability control and all the other good stuff including tire pressure sensors.



[/quote]two in my M&P. I wonder if that means that every time a round is chambered it is actually set back a bit or does it all happen at once after a number of times of chambering the same round.



Seems like Kabooms were highly associated with the .40 cal. Glocks. Set back could explain that. Anybody hear of bullet set back in the 9mm Glocks?



How about 9mm Sigs, Berettas, or H&Ks?
I think the reason that there is more documentation on Kabooms in 40's especially Glocks is because they have been a gun used by LEO's for years. Figure how many thousands of times a day across the world a military glock or one being caried by a cop or even a security officer gets cycled ejecting the first load out of the mag only to be loaded at the top again.
 
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